1. Field of the Invention
The invention relates to a method of managing resources of one or more printing products available in a printer, for printing a document stored in the form of digital data, for example in a computer, the latter being able to control said printer, which is associated with it directly or indirectly via a network. The invention also concerns a device for implementing the method.
2. Discussion of Related Art
A computerised printer contains at least one and generally several printing product reservoirs. Some reservoirs can be integrated into one and the same cartridge. For example, a black and white inkjet printer contains a single reservoir of black ink. For a colour printer, other different colour printing products are necessary, notably cyan, magenta and yellow. On certain high-performance printers, it is possible to use printing products with different densities of these three colours. It is also possible to use other colours such as red, blue, green, white, silver and gold. The printing of a document will use all or some of the printing product or products present in the different reservoirs. Obviously, the quantity of a particular printing product used depends notably on the content of the document to be printed. A simple typed document will require a printing product of a single colour, usually black. On the other hand, an illustrated report can contain images and graphs using colours. In this case, the printer will consume at least black, blue, magenta and cyan in variable proportions.
The quantity of printing product consumed also depends on the configuration of the printer at the time of printing. Some printers make it possible to choose one printing mode amongst several possible ones, low, medium or high resolution, both in black and white and in colour. Consequently, the same printer can consume very different quantities of printing products, for the same document stored in digital form, according to the print mode selected.
The quantity of printing product consumed also depends on the physical characteristics of the printing means. It depends notably, for an inkjet printer, on the type of reservoir or cartridge used, the diameter of the ink ejection nozzles on the print head and the very nature of the printing product, the size of the droplets ejected depending on the pigments used, and therefore on the colour.
The quantity of printing product consumed also depends on the characteristics of the paper used. For example, a heavyweight glazed paper will receive a larger quantity of printing product than an ordinary paper.
Finally, it should be noted that the quantity of printing product consumed also depends on the characteristics of the environment: relative humidity, pressure, temperature, etc. These characteristics are unstable by nature and falsify predictions. All the others can be predetermined or known.
U.S. Pat. No. 5,636,032 describes a system for estimating the number of pages which a printer is capable of printing. When the document is stored in the form of digital data, it is converted in order to constitute a table describing a monochromatic component of the document in the form of pixels. Reading such a table makes it possible, in the case of an inkjet printer, to control the ejection of the droplets of liquid printing product at predetermined locations on the sheet of paper, constituting the coordinates of the different pixels. It is said that a pixel is xe2x80x9cswitched-onxe2x80x9d in such a table if the cell corresponding to this pixel contains an item of information indicating that a droplet of printing product must be ejected at this pixel location.
According to the teachings of this prior patent, at the very moment of printing of one of the pages, the number of switched-on pixels in this page is counted and the or each quantity of printing product used for printing is deduced. To this end, for each ink reservoir which can be used by the printer, the mean volume of ink necessary for printing a pixel has been stored. However, the process can produce only a relatively imprecise estimation of the quantities needed since it is implemented simultaneously with the printing of a page. Estimation therefore assumes that all the pages which remain to be printed will require the same quantity of the printing product as the previous one. Such is not always the case, in practice.
Independently of such an estimation process, some printers are provided with means of measuring the or each quantity of printing product available in a reservoir or cartridge compartment in the course of use. Such a printer is for example described in the application PCT 97/00366. If the printer is connected to a computer, the measurements can be transmitted to it via an interface card and can be processed and/or displayed on a control screen of this computer.
The main object of the invention is to improve the management of the resources of one or more printing products used by the printer, notably in connection with the computer, by combining the advantages of a prediction of the or each quantity of printing product necessary for printing a document and an actual measurement of the or each quantity of printing product available in the reservoir or reservoirs of the printer at the moment when it is wished to print.
More precisely, the invention concerns a method of managing the resources of at least one printing product available in a printer, characterised in that it consists of predicting the quantity of said printing product necessary for printing a document stored in the form of digital data by describing this document by pixels and counting the switched-on pixels corresponding to said printing product, also measuring, before printing, the quantity of printing product actually available in a corresponding reservoir of said printer, comparing the predicted quantity and the measured quantity and, according to this comparison, at least sending a message and/or triggering the implementation of a processing.
Amongst the messages which can be displayed, there can be mentioned not only the prediction itself of the quantities of printing products necessary for printing a document under consideration but also, by comparison with the available quantity or quantities, information on the possibility or impossibility of actually printing the document without having to change at least one reservoir. The information broadcast can also indicate the number of copies of the document which is possible to print without having to change at least one reservoir, or, failing this, the number of the page of the document or of the nth copy which it will be possible to print without intervention.
Amongst the processings which it is possible to envisage from the comparison of the predicted quantities and the measured quantities, it is notably possible to mention the prohibition on printing or the automatic change to an economical printing mode making it possible to satisfy the user requirement. In addition, as will be seen later, correction factors can be produced and used so that a predicted quantity is as close as possible to a measured quantity of an actual consumption of a printing product. The comparison can therefore automatically and unbeknown to the user trigger the implementation of a processing updating the correction factor or factors. These correction factors make it possible notably to take into account overall the characteristics which have an influence on the quantity of printing product consumed and which are unstable or impossible to parameterize, notably the environmental characteristics (relative humidity, pressure, temperature, etc) and the usual tolerances of the components, such as for example the diameter of the ejection nozzles, or the degree of filling of a reservoir.
The method which has just been set out can preferably be essentially implemented in a computer connected to a printer. Moreover, it is more and more frequent to use computers in a network. Under these conditions, if a computer contains a document stored in digital form, it will be possible to have this document printed by a specific printer connected to another computer in the network. The prediction can be calculated by the computer containing the document before the latter is transmitted to the other computer specifically connected to the printer in question. In this case, the necessary parameters relating to the characteristics of the printer and the printing products and those relating to those of the printing mode can be exchanged by the network between the computers. In the same way, the correction factors and the levels can be exchanged between computers.
In order to prevent the representation of the monochromatic component or components of said document in the form of pixels occupying excessively large amounts of space in the memory of the computer, the method according to the invention is supplemented by the fact that an aforementioned table of limited capacity is created, less than the capacity necessary for describing the monochromatic component or components of said document. Groups of pixels of said monochromatic component are entered therein successively and the number of switched-on pixels is counted each time until all of said monochromatic component has been entered in said table and all its switched-on pixels have been counted.
Preferably, each table of limited capacity is created from digital data representing adjacent bands of the document.
In order to apply, to the digital data represented in the form of pixels, corrections which are desirable for printing, by using known correction algorithms, the method according to the invention makes provision for selecting broadened bands, overlapping, of said document. From digital data corresponding to these broadened bands, at least one enlarged table is created, allowing an image reprocessing entailing a modification of the illuminated pixels. Consequently, the enlarged table is modified by applying a known correction algorithm and the counting of the switched-on pixels corresponding to the excess part of the enlarged table, that is to say the overlapping part of the bands, is excluded.
In the case of a colour printing, as many enlarged tables as there are colours are created, each describing a monochromatic component of the document. A correction algorithm is applied, in a manner known per se, to each table in order to separately count the switched-on pixels so as to predict the different quantities of printing products necessary, of all the colours concerned, for printing part of the document corresponding to the band. After which the tables, reset to zero, receives the pixels of the following band.
When the switched-on pixels have been counted, it suffices to multiply their number by a value representing an elementary quantity of the printing product. In the case of an inkjet printer, the value in question represents the value of a droplet of printing product ejected each time by the print head. Obviously, this value depends on the print product, as indicated previously. It also depends on the type of printer and/or on the type of print head. A computer can easily contain in memory a set of such values taking into account all the equipment and products available on the market and it will be in a position to measure one of them according to an actual combination of such parameters.
With regard to the actual measurement of the quantity or quantities of printing products available in the corresponding reservoir or reservoirs, it will be possible, for each reservoir, to arrange a capacitive arm including said reservoir, apply an alternating signal to this capacitive arm and analyse a resulting signal in order to derive therefrom the said quantity of printing product actually available in this reservoir.
In addition, the successive measurements of the quantity or quantities of printing product actually available can be used for improving the prediction process.
To do this, the method is also characterised in that it consists of allocating a correction factor to the quantity or quantities of printing product predicted for the printing of a document, respectively, comparing, after actual printing of the corresponding document, the quantity or quantities predicted with the quantity or quantities or product actually consumed, respectively, reupdating the correction factor or factors in order to make the predicted quantity or quantities correspond to the quantity or quantities consumed, and using the new correction factor or factors for the following prediction.
Moreover, the user may be led to remove from the printer a reservoir still containing a certain quantity of printing product and replacing it with another similar reservoir containing another printing product, for example in order to print in a different colour. The invention makes it possible to manage the use of all these reservoirs for a total use of the printing products which they contain, also make it possible to recognise them automatically when they are reinstalled on the printer.
More precisely, the method is characterised in that it also consists of storing the quantities of printing products contained in several interchangeable reservoirs and the corresponding correction factors, measuring the quantity or quantities of printing product available, for example, before printing a document, comparing the stored quantity or quantities with the corresponding measured quantity or quantities if at least one difference appears, determining whether the measured quantity or quantities correspond to a reservoir or cartridge already used and, in the affirmative, reusing the corresponding correction factor or factors.
The method can be implemented at least partly in the computer connected to the printer. Where several computers are connected in the network and the printer is connected to one of them, the method can be implemented partly in the computer connected to the printer and partly in a second computer connected by the network to the first computer, this second computer being one which has in memory a document to be printed. For example, the method can be characterised in that said first computer (connected to the printer) contains in memory the quantity or quantities of printing products actually available and the correction factor or factors, and in that it implements the operations of measuring the quantity or quantities of printing product available as well as the operations of reupdating the corresponding correction factors, and in that said second computer implements the operations of predicting the quantity or quantities of printing products for printing said document, the operations for producing the information necessary for printing the document and the operations for transmitting this information via said network and said first computer. The necessary data are exchanged by the network between the two computers.
Naturally, the invention also concerns a device for managing the resources of at least one printing product available in a printer, characterised in that, it comprises means of predicting the quantity of said printing product necessary for printing a document stored in the form of digital data, these prediction means describing this document by pixels and counting the illuminated pixels corresponding to said printing product, means for measuring, before printing, the quantity of printing product actually available in a corresponding reservoir of said printer, means for comparing the predicted quantity and the measured quantity and means for at least sending a message and/or triggering the implementation of a processor, according to this comparison.